1. Field of the Invention
The present invention relates to a chip package, and more particularly, to an improved bottom lead semiconductor package.
2. Background of the Related Art
FIG. 1 illustrates a cross-sectional view of a bottom lead semiconductor package which is disclosed in U.S. Pat. No. 5,428,248, commonly assigned to the same assignee of the present application. The package includes a plurality of leads 2, each including a substrate mounting lead portion 2a, which is mounted at a lower surface of each thereof to a substrate (not shown), and a chip connection lead portion 2b respectively bent upwardly extending from the corresponding substrate mounting lead portion 2a. A semiconductor chip 1 is fixedly attached to respective upper surfaces of the substrate mounting lead portions 2a by an adhesive 3. A plurality of conductive wires 4 electrically connects chip pads 1a on the chip 1 to the chip mounting lead portions 2b. A molded resin compound covering a certain area of the package including the conductive wires 4, the chip 1 and the lead portions 2a, 2b of the leads 2 to form a complete package body 5.
The respective lower surfaces of the substrate connection lead portions 2a are molded but exposed through the lower surface of the package body 5 so that a solder 6 (not shown) may be formed on each of the lower surfaces of the substrate connection lead portions 2a. A substrate connection lead portions 2a are so low so as to be even with the lower surface of the package body 5, which causes various disadvantages. When the lower surface of the package body is fixedly attached to an upper surface of a printed circuit board, heat emission poses a problem. Further, a difference in thermal expansion coefficient between the substrate connection lead portions and the substrate may cause a rupture of the adhered portions. Moreover, when mounted on a printed circuit board, it is very difficult to carry out an external detection for checking a failure, such as a mounting defect.
The above references are incorporated by reference herein where appropriate for appropriate teachings of additional or alternative details, features and/or technical background.